2020 Fiscal Year Research-status Report
Design and development of spin-torque-oscillator and recording media for microwave assisted magnetic recording
| Project/Area Number |
19K05257
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
S.Amin Hossein 国立研究開発法人物質・材料研究機構, 磁性・スピントロニクス材料研究拠点, 主幹研究員 (10621758)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | magnetic recording / spin torque oscillator / spin accumulation / spin polarization / granular media |
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| Outline of Annual Research Achievements |
Microwave assisted magnetic recording (MAMR) is a promising technology to overcome the stagnated areal density increase of hard disk drives (HDD). However, its most essential part, “spin-torque-oscillator (STO)”, has not been yet realized. The STO device for MAMR should oscillate at a frequency>20 GHz at a small current density. We proposed and demonstrated a novel STO, all-in-plane (AIP)-STO, consisting of a spin-injection-layer (SIL) and a field-generating-layer (FGL) separated with a metallic spacer. We employed micromagnetic simulations and designed materials properties suitable for SIL and FGL, such as spin polarization, saturation magnetization and damping, which results in the oscillation of AIP-STO at the frequencies above 20 GHz. Based on these results, we experimentally developed AIP-STO by using Fe20Ni80 as SIL and Fe67Co33 as FGL and investigated its oscillation behavior in detail. The novel achievements in this work pave a way to use AIP-STO in the practical application for microwave assisted magnetic recording.
The second fold of this research is design and development of media material for the next generation energy assisted magnetic recording with areal density beyond 4 Tbit/in2. We developed TEM image based micromagnetic simulator and designed media for 3-dimensional magnetic recording. Moreover, we investigated the effect of underlayer and segregant to develop nanogranular FePt-based media with sufficiently large out-of-plane coercivity and small in-plane magnetization which are crucial for the media for the next generation recording technology.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
As it was proposed in the research proposal, the first goal of the project is development of a novel STO which oscillates at the frequencies above 20 GHz using a small current density. In addition, the STO should have a thickness of smaller than 25 nm for practical application. In this research, by combining advanced micromagnetic simulations and experimental approach we have succeeded this goal via development of all-in-plane STO. Moreover, we are now developing new techniques in magnetization dynamics analysis of STO using injection locking to an external magnetic field. In addition, we have employed TEM-based micromagnetic simulator and designed and developed granular media for the next generation energy assisted magnetic recording. Currently, we are working on the experimental development of the designed granular media proposed by micromagnetic simulations as was stated as the second goal of the research proposal. Hence, our research is progressing smoothly in line with the research proposal.
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| Strategy for Future Research Activity |
In the remaining time of this research, we will further optimize all-in-plane STO to reduce the current density (below 1.0×108 A/cm2) required for oscillation with frequencies above 20 GHz for MAMR applications. We will continue evaluating the magnetization dynamics of the AIP-STO using our recently demonstrated novel technique using injection locking to an external magnetic field. An accurate analysis of the magnetization dynamics of FGL is important for the practical application.
The second fold of our remaining task is development of granular media for the next generation of energy assisted magnetic recording to realize HDD with areal density beyond 2 Tbit/in2. For this purpose, we will continue working on the design of double-layered FePt media for the 3 dimensional magnetic recording. We will employ micromagnetic simulation to design the degree of ordering and strength of antiferromagnetic coupling of double-layered media for 3D magnetic recording. For this purpose, we will use our developed micromagnetic models based on STEM images of FePt-based media. Base don this, we will develop granular media experimentally which has properties such a large out-of-plane coercivity, minimum in-plane component of magnetization, and grain size of below 6nm without bimodal distribution of the grain size. We trust the research output of this work will have a great impact not only in academic point of view but also in HDD industries.
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| Causes of Carryover |
新型コロナウイルス感染拡大の影響による研究計画の一部延期により使用計画を来年度に延期したため。消耗品の執行に充てる予定である。
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